Multilayer electronic component, method of manufacturing the same and method of measuring characteristics of the same

Abstract: Disclosed herein is a multilayer electronic component (10) having one major surface (13) which can be widely utilized as a mounting surface for another electronic component to be composed with the same. A mother laminate (17) to be cut along a prescribed cutting line for obtaining a plurality of multilayer electronic components (10) is prepared, and a groove (18) is formed in the mother laminate (17) along the cutting line. External electrodes (15) are formed on side surfaces of the groove (18), and thereafter the mother laminate (17) is divided in the position of the groove (18), to obtain a plurality of multilayer electronic components (10) which are independent of each other. A number of multilayer electronic components (10) can be efficiently manufactured, while characteristics of the respective multilayer electronic components (10) can be efficiently measured in the state of the mother laminate (17).

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a multilayer electronic component which is provided in its interior with internal circuit elements, a method of manufacturing such multilayer electronic components and a method of measuring characteristics thereof, and more particularly, it relates to an improvement in a mode of formation of external electrodes in such a multilayer electronic component. Description of the Background Art A multilayer electronic component such as a multilayer capacitor, a multilayer inductor, a multilayer circuit board or a multilayer composite electronic component, for example, comprises a laminate which is formed by stacking a plurality of insulating sheets with interposition of internal circuit elements such as conductor films and/or resistor films. The insulating sheets are typically prepared from ceramic sheets. Fig. 6 is a perspective view showing the appearance of a conventional multilayer electronic component 1, which is of interest to the present invention. The multilayer electronic component 1 comprises a laminate 2, which is formed by stacking a plurality of insulating sheets with interposition of internal circuit elements (not shown). External electrodes 3 are formed on four side surfaces, for example, of the laminate 2 respectively. These external electrodes 3 are electrically connected with the internal circuit elements which are positioned in the interior of the laminate 2. While the external electrodes 3 are formed by applying proper metal films to specific portions of the respective side surfaces of the laminate 2, parts of the external electrodes 3 necessarily extend toward upper and lower major surfaces of the laminate 2 with relatively wide areas. Such a multilayer electronic component 1 is surface-mounted on a proper circuit board through the external electrodes 3, in the form of a chip. In the aforementioned multilayer electronic component 1, however, the external electrodes 3 are formed to extend toward the upper and lower major surfaces of the laminate 2 with relatively wide areas. When another electronic component is mounted on either major surface of the multilayer electronic component 1 to be composed with the same, an area capable of mounting such an electronic component is restricted. In order to manufacture such multilayer electronic components 1, the laminate 2 is independently prepared for each multilayer electronic component 1 and then provided with the aforementioned external electrodes 3, while the same is subjected to formation of a resistor film on its surface, trimming of the resistor film, measurement of electric characteristics, formation of an overcoat and the aforementioned mounting of another electronic component at need. However, it is relatively complicated and difficult to carry out such steps following manufacturing of the multilayer electronic component 1 on each independent laminate 2 in high accuracy. Thus, implementation of a further efficient method is awaited in order to obtain a number of multilayer electronic components 1, in particular. EP 0 582 881 Al, which is a non-prepublished prior art document in the sense of Article 54(3) EPC, relates to a multi-layer electronic component, a method of manufacturing the same and a method of measuring the characteristics thereof. The multilayer electronic component reduces the arrangement pitches for external electrodes by means of via holes filled up with conductive materials which are provided in a mother laminate in positions parted by cutting. The conductive materials define external electrodes of the multi-layer electronic components obtained by cutting the mother laminate and extend into the mother laminate. EP 0 535 995 A2 relates to a method of efficiently forming external electrodes on multi-layer ceramic capacitors in desired thickness. Cutting grooves are formed in a block along surfaces to provide it with external electrodes for dividing the block into individual chips while metal paste for forming external electrodes is cast into the cutting grooves and dried so that the metal paste filling up each of the cutting grooves is cut with a blade to be divided into two. Parts of the metal paste thus being divided with the blade define external electrodes. Starting from this prior art, it is the object of the present invention to provide a multi-layer electronic component having a wider area for mounting another electronic component to be composed with same, to provide a method for efficiently manufacturing a plurality of multi-layer electronic components, and a method for efficiently measuring characteristics of a plurality of multi-layer electronic components. This object is achieved by a multi-layer electronic component according to claim 1, by a method of manufacturing multi-layer electronic components according to claim 6, and by a method of measuring characteristics of multi-layer electronic components according to claim 11. The multilayer electronic components can be shipped in a state taken in an intermediate stage of the aforementioned method of manufacturing multilayer electronic components or in the method of measuring characteristics thereof, i.e., in the form of an aggregate of the multilayer electronic components consisting of the mother laminate provided with the groove. According to the inventive multilayer electronic component, the external electrode is formed to extend from halfway the thickness direction on the side surface of the laminate only toward the first major surface, whereby the overall area of at least the second major surface of the laminate can be widely utilized as a mounting surface for another electronic component to be composed with the same. Thus, it is possible to increase density in mounting of the component. According to the inventive method of manufacturing multilayer electronic components, the external electrodes can be applied in the state of the mother laminate for providing a plurality of multilayer electronic components while the mother laminate can be subjected to formation of resistor films, trimming of the resistor films, formation of overcoats and mounting of other electronic components to be composed with the multilayer electronic components at need, whereby these steps can be efficiently carried out in high accuracy. Thus, the manufacturing method according to the present invention is particularly advantageously applied to manufacturing of a number of multilayer electronic components. According to the inventive method of measuring characteristics of multilayer electronic components, the groove is formed in the mother laminate for providing a plurality of multilayer electronic components so that the plurality of multilayer electronic components are electrically independent of each other while the external electrodes are also electrically independent of each other for the respective multilayer electronic components, whereby it is possible to measure electric characteristics of the respective multilayer electronic components in a state mechanically integrated with each other as the mother laminate. Thus, it is not necessary to handle a plurality of multilayer electronic components which are mechanically independent of each other, whereby electric characteristics of a number of multilayer electronic components can be efficiently measured by screening, for example. When the multilayer electronic components are shipped in the aforementioned state taken in an intermediate stage of the manufacturing method, i.e., in the form of an assembly of the multilayer electronic components comprising the mother laminate provided with the groove to be subjected to characteristic measurement, the user can take out the respective multilayer electronic components by simply dividing the mother laminate along the groove. It is to be noted that the respective multilayer electronic components can be mounted on circuit boards with no problem in this case since characteristic measurement therefor can be already completed while the assembly of such multilayer electronic components can be further readily packed and handled as compared with multilayer electronic components which are in discrete states. The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing the appearance of a multilayer electronic component 10 according to an embodiment of the present invention; Fig. 2 is a perspective view showing a part of a mother laminate 17 which is prepared for obtaining the multilayer electronic component 10 shown in Fig. 1; Fig. 3 is a sectional view showing a part of the mother laminate 17, appearing in Fig. 2, provided with external electrodes 15 in an enlarged manner; Fig. 4 is a sectional view corresponding to Fig. 3, showing a mother laminate 17a which is prepared according to another embodiment of the present invention; Fig. 5 is a sectional view corresponding to Fig. 3, showing a mother laminate 17b which is prepared according to still another embodiment of the present invention; and Fig. 6 is a perspective view showing the appearance of a conventional multilayer electronic component 1 which is of interest to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a perspective view showing the appearance of a multilayer electronic component 10 according to an embodiment of the present invention. This multilayer electronic component 10 is mounted on a proper circuit board in the form of a chip as illustrated. Fig. 1 shows the multilayer electronic component 10 in a state upwardly directing a first major surface 11 to be mounted on such a circuit board. The multilayer electronic component 10 comprises a laminate 12, which is formed by stacking a plurality of insulating sheets with interposition of internal circuit elements (not shown). In addition to the first major surface 11, the laminate 12 comprises a second major surface 13 which is opposed to the major surface 11, and side surfaces 14 coupling these major surfaces 11 and 13 with each other. External electrodes 15 are applied to respective ones of, e.g., four side surfaces 14 of the laminate 12. These external electrodes 15 are electrically connected with the external circuit elements, although such connection is not shown in Fig. 1. While steps 16 are formed on the side surfaces 14 of the laminate 12, the reason for formation of such steps 16 is clarified in later description of the inventive manufacturing method. In order to obtain the aforementioned multilayer electronic component 10, prepared is a mother laminate 17, which is only partially shown in Figs. 2 and 3. The mother laminate 17 is provided with grooves 18. The mother laminate 17, which is cut along cutting lines (not shown) corresponding to the positions of the grooves 18 for providing a plurality of multilayer electronic components 10, is formed by stacking a plurality of mother insulating sheets with interposition of internal circuit elements 19 and 20 for the respective multilayer electronic components 10 so that these internal circuit elements 19 and 20 are distributed in respective regions divided by the cutting lines. The internal circuit elements 19 and 20 shown in Figs. 2 and 3 are mere examples, and the internal circuit elements are provided by conductor films and/or resistor films, via holes and the like, in addition to those shown in the figures. In order to obtain the aforementioned mother laminate 17, the following steps are carried out, for example. According to this embodiment, the mother laminate 17 is provided by stacking mother insulating sheets which are formed by ceramic sheets. First, sheet forming is performed by a doctor blade coater or the like, to obtain ceramic green sheets for serving as mother insulating sheets. Specific ones of these ceramic green sheets are provided with conductor films and/or resistor films for forming the internal circuit elements 19 and 20, and via holes at need. Then, the mother insulating sheets are stacked with each other and pressed. Thus, the mother laminate 17 is obtained. Then, the grooves 18 are formed in the mother laminate 17 by a dicing saw, for example. Due to such formation of the grooves 18, portions enclosed with the grooves 18 for defining the respective multilayer electronic components 10 are electrically independent of each other. Then, the external electrodes 15 are applied onto side surfaces of the grooves 18. The external electrodes 15 are formed by applying proper metal paste with a dispenser, for example, and the metal paste is thereafter dried. The external electrodes 15 are applied not to be in contact with each other, whereby the same are electrically independent of each other. According to this embodiment, the external electrodes 15 are formed to extend from positions to be in contact with bottom surfaces of the grooves 18 toward the upper major surface 11 of the mother laminate 17, as clearly shown in Fig. 3. Figs. 2 and 3 show the external electrodes 15 and the internal circuit elements 19 in states electrically connected with each other. Then, notches 21 and 22 are preferably formed in the bottom surfaces of the grooves 18 and the lower major surface 13 of the mother laminate 17 which is opposed thereto. Either of the notches 21 and 22 may be omitted. Then, the mother laminate 17 is fired to simultaneously sinter the ceramic material forming the mother insulating sheets and the external electrodes 15. Thereafter the surface of the mother laminate 17 is subjected to formation of a conductor film and/or a resistor film, formation of an overcoat and application of solder resist at need. Further, the external electrodes 15 or another conductor film is plated at need. After the aforementioned steps are completed, electric characteristics of the respective multilayer electronic components 10 can be measured through the external electrodes 15, since the plurality of multilayer electronic components 10 included in the mother laminate 17 are electrically independent of each other. After such measurement of the electric characteristics, other electronic components are mounted at need on those of the multilayer electronic components 10 which are determined as non-defectives, to be composed with the same. Each of such electronic components is mounted on the second major surface 13 of each laminate 12 shown in Fig. 1. The multilayer electronic components 10 may be shipped in this stage. Then, the mother laminate 17 is completely divided in the positions of the grooves 18, in order to obtain a plurality of multilayer electronic components 10 which are mechanically independent of each other. The mother laminate 17 can be readily divided along the grooves 18, like a chocolate bar. The aforementioned notches 21 and 22 are adapted to facilitate such division. Thus, the multilayer electronic component 10 shown in Fig. 1 is obtained. As understood from the above description, the steps 16 result from formation of the aforementioned grooves 18. The multilayer electronic component 10 is then cased at need, in order to cover another electronic component which is mounted on the second major surface 13 of the laminate 12. The aforementioned method of manufacturing multilayer electronic components 10 can be modified as follows: For example, the firing step may be carried out in advance of the step of forming the notches 21 and 22, that of applying the external electrodes 15, or that of forming the grooves 18. In this case, a step of baking the external electrodes 15 is separately carried out after application/drying. When the external electrodes 15 are applied after the firing step, the external electrodes 15 may be formed by evaporation or sputtering. When the notches 21 and 22 are formed after the firing step, further, the same can be formed with a laser beam. The external electrodes 15 may be applied after formation of the notches 21 and 22. The mother laminate 17 may be divided along the grooves 18 with no previous formation of the notches 21 and 22, while portions between the bottom surfaces of the grooves 18 and the lower major surface 13 of the mother laminate 17 may be cut with a dicing saw which is smaller in edge thickness than that employed for forming the grooves 18. The external electrodes 15 may be in a state connected with each other between adjacent ones of the multilayer electronic components 10 in the stage of application thereof. In order to make the external electrodes 15 electrically independent of each other, a dicing saw having an edge thickness which is smaller than the width of each groove 18 or a laser beam may be applied, for example. Further, the notches 21 may be simultaneously formed by such application of the dicing saw or the laser beam. In addition, the external electrodes 15 may be applied after the mother laminate 17 is divided along the grooves 18. In this case, the mother laminate 17 may be divided before firing to be then provided with the external electrodes 15 and simultaneously fired with the same, or may be divided after firing to be then provided with the external electrodes 15, which in turn are baked. In these cases, characteristics are measured every product. Figs. 4 and 5 are sectional views corresponding to Fig. 3, showing mother laminates 17a and 17b which are prepared according to further embodiments of the present invention respectively. Referring to Figs. 4 and 5, elements corresponding to those shown in Fig. 3 are denoted by similar reference numerals, to omit redundant description. The features of the embodiments shown in Figs. 4 and 5 reside in modes of formation of external electrodes 15a and 15b respectively. The external electrodes 15a and 15b shown in Figs. 4 and 5 do not reach bottom surfaces of grooves 18. Thus, it is possible to reliably prevent the external electrodes 15a and 15b from unintendedly entering conducting states between adjacent multilayer electronic components 10. Further, the external electrodes 15b shown in Fig. 5 do not reach a first major surface 11. According to this embodiment, therefore, it is possible to also utilize the first major surface 11 as a mounting surface for other electronic components, with no interference by the external electrodes 15b. According to the present invention, the insulating sheets are not restricted to ceramic sheets but may be prepared from sheets of another material.

Claims: A multilayer electronic component, comprising: a laminate (12), being formed by stacking a plurality of insulating sheets with interposition of an internal circuit element (19, 20), said laminate (12) having first and second opposite major surfaces (11, 13) and plane side surfaces (14) coupling said major surfaces (11, 13) with each other; and an external electrode (15, 15a, 15b) being electrically connected with said internal circuit element (19, 20) and formed on portions of the side surface (14) of said laminate (12), characterized in that said side surfaces (14) of said laminate (12) are provided with a circumferential step (16) for defining a first portion of said laminate (12) being closer to said first major surface (11) and a second portion being closer to said second major surface (13), said external electrode (15, 15a, 15b) being formed only on said first portion; and said external electrode (15, 15a, 15b) is formed to extend on said first portion of said side surface (14) of said laminate (12) only toward said first major surface (11). A multilayer electronic component in accordance with claim 1, wherein said external electrode (15) is formed to extend from a position reaching said step (16) to a position on said first major surface (11). A multilayer electronic component in accordance with claim 1, wherein said external electrode (15) is formed not to reach said step (16) but extend to a position on said first major surface (11). A multilayer electronic component in accordance with claim 1, wherein said external electrode (15) is formed to reach neither said step (16) nor said first major surface (11). A multilayer electronic component in accordance with claim 1, wherein said laminate (12) is formed by an integral sintered body of ceramic. A method of manufacturing multilayer electronic components according to one of claims 1 to 5, comprising the steps of: preparing a mother laminate (17, 17a, 17b), to be cut along a prescribed cutting line, said mother laminate being formed by stacking a plurality of mother insulating sheets with interposition of internal circuit elements (19, 20) for respective said multilayer electronic components (10) for distributing said internal circuit elements (19, 20) in respective regions being divided by said cutting line; and forming a groove (18) in said mother laminate (17, 17a, 17b) along said cutting line; characterized by the following steps: applying the external electrodes (15, 15a, 15b) on side surfaces of said groove (18) to be electrically connected with said internal circuit elements (19, 20); and dividing said mother laminate (17, 17a, 17b) in the position of said groove (18). A method of manufacturing multilayer electronic components in accordance with claim 6, wherein said mother insulating sheets are ceramic green sheets, said method further comprising a step of firing said mother laminate (17, 17a, 17b). A method of manufacturing multilayer electronic components in accordance with claim 6, further comprising a step of forming a notch (21, 22) in at least either a bottom surface of said groove (18) or a major surface of said mother laminate (17, 17a, 17b) being opposed to said bottom surface, to be along said groove (18). A method of manufacturing multilayer electronic components in accordance with claim 6, wherein said step of applying said external electrodes (15, 15a, 15b) comprises a step of applying said external electrodes (15, 15a, 15b) to both of opposite side surfaces of said groove (18) independently of each other. A method of manufacturing multilayer electronic components in accordance with claim 6, wherein said step of applying said external electrodes (15, 15a, 15b) comprises the steps of applying metal paste materials for defining said external electrodes (15, 15a, 15b) to both of opposite side surfaces of said groove (18) to be connected with each other in such a manner that same form a bridge between said opposite side surfaces, dividing the same into separate independent external electrodes, and dividing the substrate to form each individual component. A method of measuring characteristics of multilayer electronic components according to one of claims 1 to 5, characterized by the steps of: preparing a mother laminate (17, 17a, 17b), to be cut along a prescribed cutting line, said mother laminate being formed by stacking a plurality of mother insulating sheets with interposition of internal circuit elements (19, 20) for respective said multilayer electronic components (10) for distributing said internal circuit elements (19, 20) in respective regions being divided by said cutting line; forming a groove (18) in said mother laminate (17, 17a, 17b) along said cutting line; applying the external electrodes (15, 15a, 15b) on side surfaces of said groove (18) to be electrically connected with said internal circuit elements (19, 20); and measuring electric characteristics of respective said multilayer electronic components (10) in this state through said external electrodes (15, 15a, 15b). A method of measuring characteristics of multilayer electronic components in accordance with claim 11, wherein said step of applying said external electrodes (15, 15a, 15b) comprises a step of applying said external electrodes (15, 15a, 15b) to both of opposite side surfaces of said groove (18) independently of each other.

Inventors: KUBOTA KENJI C O MURATA MANUFA, SAKAI NORIO C O MURATA MANUFAC, KUBOTA, KENJI, SAKAI, NORIO, KUBOTA, KENJI, C/O MURATA MANUFACTURING CO., LTD., SAKAI, NORIO, C/O MURATA MANUFACTURING CO., LTD.
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1994
Main classification: H01G4
IPC codes: H05K3, H01G4, H05K1, H01C1, H01F17, H01L23